In recent years, as one of the methods for synthesizing liquid fuel from natural gas, there is a method of reforming natural gas to produce synthesis gas having carbon monoxide gas and hydrogen gas as main components, and synthesizing hydrocarbons using a catalyst with this synthesis gas as source gas. Such a synthesis reaction is referred to as the Fischer-Tropsch synthesis reaction (hereinafter referred to as “FT synthesis reaction”).
Additionally, the Gas-To-Liquids (GTL: liquid fuel synthesis) technique of hydrorefining the hydrocarbons obtained in this way to produce liquid fuel products, such as naphtha (raw gasoline), kerosene, gas oil, and wax has been developed.
In hydrocarbon synthesis apparatuses for the FT synthesis reaction used for this GTL technique, hydrocarbons are synthesized by performing the FT synthesis reaction on the carbon monoxide gas and the hydrogen gas in the synthesis gas inside a bubble column slurry bed reactor in which a slurry having solid catalyst particles suspended in a medium liquid is held. In this case, as the hydrocarbon synthesis apparatuses, upflow types in which the synthesis gas that is a feedstock is introduced from a lower portion of the bubble column slurry bed reactor are used (for example, PTL 1).
Generally, for the purpose of uniformly dispersing a catalyst in a reactor, synthesis gas is sprayed and introduced toward all of the bottom surface of the reactor. The synthesis gas sprayed in this way moves up within the reactor as bubbles, the slurry is stirred by the upward movement energy of the bubbles and a mixed and flowing state of the slurry is maintained.
Meanwhile, a synthesis gas spraying part is constituted of a plurality of header tubes in which openings are formed at equal intervals. Although powdering of the catalyst included in a slurry occurs due to the spraying of the synthesis gas within the reactor (generation of fine powder), this powdering is great at the time of the start of operation, and becomes gradual after the elapse of a certain given time. That is, a shift from initial powdering to steady powdering is made. A shift time is determined depending on the kinetic energy of the synthesis gas spraying into a reaction vessel. If a lot of such fine power is generated, this becomes a cause of blocking a filter that separates the catalyst, and hydrocarbons generated within the reactor.
Meanwhile, if the mesh of the filter is made equal to greater than the size of the fine powder particles in order to avoid the blocking, the powdered catalyst passes through the filter and flows out of the reactor. Therefore, there is a concern that the catalyst may be lost. It is necessary to reduce the kinetic energy of the synthesis gas sprayed into the reactor to a predetermined numerical value in the light of such a problem.
A tubular shroud is attached to each of the openings of the synthesis gas spraying part so as to surround the periphery of the opening. This weakens the momentum of the synthesis gas sprayed from these openings, and the kinetic energy of the synthesis gas is reduced.